https://www.mathpapa.com/algebra-calculator.html

has "Show Keypad" but typing on keyboard is quicker.

Type your expression/equation/functions/points then Enter or click "Calculate it!"
Multiple things separated by ;
Pasting "math" stuff into it sometimes needs editing.
Check its "re=write" of your text box. It looks better.

Arithmetic:
2*-3    * displays as · (raised dot)   cf. Windows Calc.
123.345*345.456
3/4     / becomes fraction bar
(5+2)/2   PEMDAS, so need to parenthesize numerator upon typing (can delete them after)
4/3*5   "stays" in denominator. Rt arrow or click to get out of denominator.
pi     becomes π  but in the rewrite is 3.141593
e                    but in the rewrite is 2.718282
sqrt   becomes √ with extending bar. "stays" in it, Rt. arrow or click to get out.
^   goes up into exponent   6^3   To "stay" in the exponent area, use (): 6^(x+2)
() {} [] can be used for grouping
Mixed numbers: 23 4/5  (a space between the integer and the fraction)
Divide by 0: infinity
Square root of negative number: NaN ("not a number")
  but understands complex numbers i (multiply and divide them. powers of i. but not as solutions to EQs)
Percent: 45%123


Algebra:      Can use any single letter as variable.
Simplify expression: 2x+3x    =5x
Evaluate expression: 2x+3x   @x=3    =15
                     2x+3y   @x=3,y=5  =21    @(3,5)
                     5x3-6x2+3x-5   @x=3   =85
FOIL-ing:  (2x+3)(x-4)        =2x2−5x−12
Factor expressions:  4x+4   =4(x+1)
                     2x2−5x−12    =(2x+3)(x-4)
Evaluate equation:   x2-4x+2=7    @x=5    7=7 True
                     x2-4x+2=7    @x=4    2≠7 False
                    3x2-4y+2=9    @(3,5)  9=9 True
                    3x2-4y+2=8    @(3,5)  9≠8 False
Solve equations: linear: 2x+3x=25    x=5
                 quadratic: 0=3x2+3x-4   shows solution(s), if any.
 Literal equations (more than one variable): solve for any variable.
   F=9/5C+32    solve for C.  Annoyances: lowercases the variables; puts in alphabetcial order.
   
Solve inequalities:  -9<4x-5<=11   
Solve compound inequalities: 3x+2>-7 and 4x+1<=-7      or

Solve system of two linear equations: 2x+3y=8 ; 5x-4y=-3

Functions: it does not understand f(x)=, must use y=.
  y=5x-4    Graphs it in 10x10
  Change graph by: Xmin:  Xmax:  Ymin:  Ymax:
  y=-3x2+3x-4   (a quadratic function)
 Many functions graphed: y=-3x2+3x-4 ; y=5x-4 ; y=3 ; y=2x ; (2,3)
 Also knows log, ln, sin, cos, tan, || (absolute value)
 Only graphs if y is a function of x. (ie. no other variable names), 
   So if you have a function h of t, change it to y of x.

Desmos.com is a better graphing webpage.

Plot points: (2,3)
Two points: (2,3);(-3,7)    Solve: slope m of line they are on.  Graph: plots them

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App.
has a problem with sqrt: use parens to keep all terms inside the sqrt