A calculation problem at the junior high school level is urgent

Let s (x+y)=a be (1) and s (x-y)=b be (2), divide (1) by (2) to get (x-y) (x+y)=a b, divide the numerator denominator to the left of the equal sign by y, and get (x y-1) (x y+1)=a b, and solve the equation as a whole by x y, and get x y=(a+b) (b-a).

From the condition, we know that x+y=s a

x-y=s/b

2x=s/a+s/b,2y=s/a-s/b；The answer is divided by the two equations, and the numerator and denominator are multiplied by ab s for the answer (a+b) (b-a).

Take the above two formulas on both sides, add and subtract the two formulas respectively, express x, y, and divide them.

s/(x+y)=a...Type 1.

s/(x-y)=b...Type 2.

Eq. 1 Eq. 2 gets (x-y) (x+y)=a b, and there is 2x (x+y)=(a+b) b

i.e. x (x+y) = (a+b) 2b

x y=(a+b) (b-a).

By deducing s=a(x+y) s=b(x-y) from the above two equations, we get ax+ay=bx-by

Both sides are divided by y at the same time, and then by moving the direction, the common factor is extracted to get x y=(a+b) (b-a).

10 grams of limescale contains calcium carbonate, which requires hydrochloric acid, magnesium hydroxide, hydrochloric acid, so the quality of hydrochloric acid is (

CaCO3 is 75% Ca(OH)2, which is 25% CaCO3 + 2HCl=CaCl2+H2O=CO2 mg(OH)2+2HCl=2H2O+mgCl2

10*75% 100 x 10*25% 58 y 1 2 x= 1 2 y=

So hydrochloric acid mass m=( +

These broken words have wasted me for a long time I was called the prince of chemistry back then, don't worry, thank you

The mass of calcium carbonate is 10 75% =

then CaCO3+2HCl=CaCl2+H2O+CO2 x100 x=

Magnesium hydroxide has a mass of 10

then mg(oh)2+2HCl=mgCl2+2H2OX58 x=

The amount of 10% hydrochloric acid required is:

(minus sixty-three) (one-ninth minus two-sevenths plus two-thirds minus four-tenths of twenty-one) = 4 21

The above equation is equal to: 74*1024*(1 37)*(Douyun 9 37) empty rotten beam*( 1 521) 38*36 37 Divide the preceding numerator and denominator to the equation.

9 Calendar 37 38*36 37 then becomes an equation for.